A great variety of cleaning compositions have been described in the art. Indeed, compositions comprising hydrogen peroxide, and/or water soluble sources thereof including peracids are widely used. In order to provide such compositions comprising peracids, it is common practice to use peracid precursors as a source of said peracids. Indeed, peracids are not commonly commercially available, and if available may not be used satisfactorily, as said peracids are not stable and tend to decompose dramatically during storage, this even before their incorporation into a composition. Compositions containing such peracids can be made by a variety of methods employing reactions between hydrogen peroxide and the corresponding peracid precursors, i.e. the corresponding acids. However, such methods are not fully satisfying. Indeed, there is a need for the development of processes for manufacturing aqueous compositions with better productivity in several respects, e.g. formulators are looking for a process which allows to incorporate higher amounts of peracids in a finished product, starting from a given amount of the corresponding precursors.
It is therefore an object of the present invention to provide a process for improving the efficiency of producing peracids.
We have now found that this object can be efficiently met by reacting a concentrated hydrogen peroxide solution with, as the precursor of the peracid, the corresponding anhydride instead of the corresponding acid. Indeed, it has been found that a faster preparation as well as a higher yield of said peracid are achieved when reacting with a concentrated hydrogen peroxide solution, the corresponding anhydride, as compared to reacting with said concentrated hydrogen peroxide solution, the corresponding acid instead of said corresponding anhydride, as said precursor of said peracid. In other words, it has been found that a process which comprises the step of reacting the corresponding precursor being in an anhydride form with a concentrated hydrogen peroxide solution leads to faster preparation of compositions comprising a higher amount of said peracid, starting from a given amount of said precursor.
An advantage of a process according to the present invention is that it allows for great flexibility in formulating and provides compositions comprising peracid suitable to be used in the most efficient manner by the consumer. Indeed, such a composition can be a raw material composition, or can be a fully formulated detergent composition comprising additional ingredients such as those commonly used in the detergent field. Preferred herein is a process which allows to provide compositions with high amounts of peracids, said compositions being in the form of emulsions. Indeed, an advantage associated with the emulsions obtained according to a process of the present invention is that such compositions not only incorporate a higher amount of a peracid, starting from a given amount of the corresponding anhydride but also allow to provide a finished product having improved stability during storage, i.e. in emulsions the rate of decomposition of peracids contained therein is reduced, as compared to compositions being not in the form of emulsions.
Processes for the preparation of compositions or even emulsions comprising a bleach have been disclosed in the art. For instance, EP-A-598170 discloses the use of emulsions to formulate compositions comprising H.sub.2 O.sub.2 and a hydrophobic bleach activator (ATC), wherein the bleach activator is kept separate from H.sub.2 O.sub.2. This patent application also discloses the possible use of a water-soluble source of H.sub.2 O.sub.2 including peracids but no indication is given about how to provide them. Indeed, although a general process for the preparation of emulsions is disclosed, none of the process steps disclosed therein indicates how to incorporate peracids, or to use peracid precursors in their anhydride form.
WO 93/0516 to Interox discloses a process for the preparation of a dilute aqueous solution comprising an hydroxyaliphatic peroxycarboxylic acid having no more than 7 carbon atoms in which in a first step a concentrated aqueous solution of said peroxycarboxylic acid precursor, i.e. an hydroxyaliphatic carboxylic acid, is mixed with a concentrated hydrogen peroxide solution in presence if necessary of a strong acid as a catalyst, in a second step the mixture is stored until the concentration of said peroxycarboxylic acid has approached its maximum; then the mixture is diluted in water. WO 93/0516 does not disclose the use of any peroxyacid precursor being in its anhydride form.
EP 188 025 mentions that the peroxymonosulphuric acid used in the compositions disclosed therein are commercially available in an aqueous solution as Caro's acid prepared by addition of concentrated hydrogen peroxide to concentrated sulphuric acid. Thus, the peracid precursors disclosed are the corresponding acids whereas in the present invention the corresponding anhydrides are used.